Age hardenable, nickel-iron-chromium-titanium alloy possessing controlled thermoelastic properties



new, 1941.

N. B. PILL'ING ET AL 2,266,432 AGE HARDENABLE,NICKEL-IRON-CHROMIUM-TITANIUM ALLOY POSSESSING CONTROLLED THERMOELASTICPROPERTIES Filed Oct. 27, 1939 EF'F'ECTIVE NICK EL: PER CENT L0 Q3 3022m0 Fzwaiumo wmak/mwmiwh CHROMIUM PER CENT no 215002 .0 FzmUEuuO wmzkmmuimr 5 T R60 Y mg m m m W T 2 M P N mm w Patented Dec. 16, 1941 'AGEHARDENABLE, NICKEL moN chao- MIUM TITANIUM ALLOY rossassmc. CONTROLLEDTHERMOELASTIC raor- ERTIES Norman B. Pilling, Westiield, and Albert M.

Talbot,,Fairhaven, N. J., assignors to The International Nickel Company,Inc., New York, N. Y., a corporation of Delaware Application October 27,1939, Serial No. 301,581

Claims.

The present invention relates to improved I age-hardenable controlledmodulus alloys and to age hardened articles of manufacture madetherefrom, and more particularly, to age harden able controlled modulusiron-nickel-chromium alloys and articles of manufacture made therefromfor use in precision devices of resilient nature.

It is well known that the accuracy of precision devices of resilientnature, for example, 'chronometers, weighing scales, etc., changes intemperature. It has been suggested that these defects could be overcomeby using materials made of alloys of substantially constant orcontrolled elastic modulus containing about 30% to 38% nickel, up to 12%chromium, and the balance iron.- It is also known that part of thechromium may be replaced by one or more of the members of the groupconsisting of tungsten, molybdenum, vanadium, aluminum and silicon inamounts ranging from traces, e. g. 001% up to 4% or even more. Thesemetals, like chromium, lower the temperature coeilicient of the modulusof elasticity of iron-nickel alloys containing about 35% nickel so thatthe coefficient'has a value of zero or is slightly negative or positiveas desired, when measured at usual temperatures. Tungsten, molybdenumand vanadium also served to increase the base hardness of the alloys.These alloys are frequently referred to as controlled or constantmodulus alloys. By constant modulus, we mean that the temperaturecoefllcient of the modulus .of elasticity is substantially zero. Alloysreferred to as "controlled modulus alloys will have a small positive ornegative value for the temperature coeiiicient of modulus of elasticityas is required to give the best overall result and will are affected byinclude those showing a zero change in modulus with temperature.Generally speaking, these modulus changes refer to changes observed attemperatures ranging from ordinary atmospheric temperatures up to about200 F. Since these alloys are austenitic, they can be hardened only bycold work and as a consequence, many potential applications have beenhindered by the fact that the alloys did not possess the high strengthand other mechanical properties required in these applications. Attemptsto obtain the desired mechanical properties by cold working about 75% to90% did not produce completely satisfactory material. when carried outinto industrial scale operation. Serious difliculties were alsoconstantly encountered in cold working the alloys to the required heavycold .into practical and economic reductions. Even excessive amounts ofcold work yield only moderately good mechanical properties and entailserious difficulties inproduction and subsequent fabrication.

Although many attempts were made to remedy the aforementionedshortcomings, none as far as we are aware, was entirely successful,produced satisfactory results and could be carried industrial scaleoperation.

We have discovered certain iron-nickel-chromium-titanium alloys whichcan be age hardened and in which the'nickel, chromium and titanium arecritically related to yield controlled or substantially constantthermo-elastic properties akin to those exhibited by the alloys of theElinvar-type but exhibiting markedly superior mechanical properties,particularly high proportional limits. Titanium is added in critical andcontrolled amounts and a compensating adjustment is made in the nickeland chromium contents in special proportions to balance said nickel andchromium against titanium and any carbon which is present. The agehardening characteristics facilitate manufacture and avoid the necessityof the excessive cold working required with e-existing materials.

t is an object of the present invention to provide improvedage'hardenable and age hardened controlled modulusiron-nickel-chromiumtitanium alloys which contain controlled andadjusted proportions of nickel, chromium and titanium and in which thenickel and chromium are balanced against the titanium and any carbonpresent in the alloy.

It is .another object of the present invention to provide improved agehardenable and age hardened iron-nickel-chromium alloys of theElinvar-type containing controlled and balanced amounts of nickel,chromium and titanium and characterized by improved mechanicalproperties, including high proportional limits and'tensile strengthwhile achieving a substantially constant or controlled temperaturecoefficient of modulus of elasticity.

I It is a furtherobject of the present invention to provide, as articlesof manufacture precision devices including resilient elements made ofspecial age hardened ferrous austenitic alloys containing controlled andspecially balanced amounts of nickel, chromium and titanium.

The invention contemplates a method of producing age-hardenable andage-hardened controlled modulus iron-nickel-chromium alloys andcontaining controlled amounts of titanium 2 2,aee,4sa

and articles of manufacture for use in precision but upon a relationshipof chromium-like metal devices of resilient nature made therefrom, andto titanium. In addition to titanium, the alloys Ds8essing substantiallyconstant thenno-elastic may contain carbon, especially in industrialpracmodulus combined with high mechanical propertice. While not anecessary element, commerties in the age hardened condition, saidprocess cial production methods often result in the introinvolving anadjustment, in special proportions duction of some carbon, e. g., alongwith the titaof the nickel content and the chromium content niumaddition alloy. Carbon may be present in to compensate for thealteration in thermoamounts up to about 0.2%, but it is preferred toelastic properties caused by the presence of maintain the carbon at lowlevels, e. g., up to titanium. m .0896, in order that: the maximumbenefits of Other objects and advantages of the present titaniumberealized. The amounts of nickel and invention will become apparent tothose skilled in of chromium or chromium-like metals are dethe art fromthe following description taken in pendent upon a relationship of carbonand titaconiunction with the accompanying drawing in nium which has beentermed herein the "nonwhich: carbidic titanium. For practical purposes,the Fig. 1 is a graph illustrating the eflect of varynon-carbidictitanium is the total titanium coning the eil'ective nickel content uponalloys content in weight percent less four times the carbon tainingsufflcient chromium to exhibit negative content in weight percent. Theeifective nickel m i nts; and content of the alloys provided by thepresent in- Flg. 2 is a graph depicting the effect of vary- 2o ventionshould be maintained within the range of ing the chromium content uponanother series about 34.5% to about 37.5%, or 39%, and the of alloysmade in accordance with the present .titanium content within the rangeof about 1% invention. to 4%. The total nickel content of the alloysBroadly stated, the inverfithgi1 prgiiges iionmay be expressed by thefollowing formula: nickel-chromium alloys 0 e var- W 1 which containcontrolled and critical amounts of Total NL'Eflectfive (Non'cubmic TDtitanium and which after age hardening heat where K has a value of about2.4. The total chrotreatmentpossess markedly increased mechanical miumpercentage is expressed by the following properties combined withcontrolled sir substanformula: tially constant thermo-elastic proper es,e. g., a .10 zero thermo-elastic coemcient. A strictly con- %Ttalcr+%Nn'mb1dic n 4% 9% stant modulus alloy is not always desirable, sinceThe alloys of the present invention hav the in practical applications,dimensional changes in approximate mmposiflon t forth in the followthestructure may require a slightly negative or m Tam positivethermo-elastic coefllcient, in order to Table I secure a minimumtemperature coefllcient for the whole device. The present inventionprovides Element Percentage alloys with constant or controlledcoefficients of modulus of elasticity over a wider range of temperaturesthan is ordinarily obtained and, in; addition, higher mechanicalproperties are obtained with greater ease of production and subsequentmanufacture. Mechanical properties, especially proportional limit whichis generally of I controlling importance in resilient elements, in Thetotal nickel content 118118113 falls within t excess of those obtainableby cold working the nge of about 36% to about 47%. As p inted ordinaryalloys are produced in the alloys pro- 011% ie e. some carbon is usuallyp e vided by the present invention. e. 8., .0 to 0.07%, and preferablyless than The compositions that have been found to deabout It is to beunderstood that carbon velop the above-mentioned desirable characteristomay e completely absent o m y be P s 0111! tics an properties areessentially alloys of iron, in traces or small amounts of the order of0.001%. nickel and chromium to which about 1% to about In addition, thealleys y 5 co tain S all 4% of titanium has been added. It has been untsof minor elements and imp r s and found that when titanium is added tothe Elinvarwhen We in the p i a i n and claims that type alloys, thethermo-elastic properties are adthe balance 18 "balance 15 Substantiallyversely affected and are not as expected or deiron, We include Withinthe e p n sired. We have discovered that the compositionminoreonstituehbs and impurities. Such 38 Cobalt, of thetitanium-containing alloys must be selectmanganese. Zirconium. silicon,aluminum, Sulfur. ed in accordance with certain special relation-Phosphorus and other elements n y P ships b tw th l i m t t t th B0 entin such materials in commercial practice. various elements must bebalanced against each Thus, the alleys may contain from traces, -5 otherinspecial proportions to control the temup to about 1% of silicon. p toabout perature coefllclent of the modulus of elasticity. a anese. up toabout 1% aluminum. etc. It has been found that the thermoelastic proper-511mm. and aluminum. is l as r e ties are not solely dependent upon thetotal nickel Often associated with the iitanium used 88.811 for a fixedchromium content ofithe alloys, as in addition material. a sa es is oten pr e the case of grdinary anoys of t Elmvaratype, for the purpose ofimproving the forgeability. As but are dependent upon the portion of thenickel pointed out hereinbefore, the chr y be nt t which ha b term dherein the eflfecreplaced by other elements which have an eifect tivenickel content. Likewise, the thermo- 701811111191) chromium-likeelastic properties for a fixed nickel content are in nts from traces,say 0.001 p to about not solely dependent upon the total percentage 4%.or even more, as is well known to those skilled of chromium-like metal,i. e., chromium plus any in the art and when we refer to chromium in thevanadium, tungsten, molybdenum, aluminum or claims we do not desire toexclude the presence silicon present as a replacement for chromium, oi!small amounts of chromium-like metals as asoeasa.

Somewhat higher mechanical properties may be above indicated or as willhave the same desired effect as chromium on the thermoelasticproperties.

In carrying the invention into practice, it is preferred to maintain thetitanium within, the

of minor elements which may be present as a.

result of commercial practice include about 0.06%

carbon, about 0.5% silicon, about.0.6% manganese, about 0.3% aluminum.

In order that those skilled in the art may have a better understandingof the present invention, illustrative examples of constant modulusalloys produced in accoi dance with the present invention are given inthe following Table H.

\ Table 11 Element Alloy 1 Alloy 2 Alloy 3 Alloy 4 Nickel "percent" 4042 44 42 Ghromium do 6 5. 4 4. 7 5. 2 Titanium .do 2. 3. 25 2. 5 Car :1do 0.06 0.06 0.06 0.00 Moly m d0 0. 45

The influence of eilective nickel content upon the temperaturecoefllcient of one series of alloys is illustrated in Fig. 1. Fig. 2shows the effect of chromium upon the temperature coemcient of themodulus of rigidity of an alloy containing 42% nickel, 2.6% titanium,0.45% molybdenum,

chromium in various amounts and the balancement at 1250 F. for 4 hoursand furnace cooled.

iron which has been subjected to an aging treat- The values given hereinfor the temperature co-, efficient of the modulus'of rigidity, i. e.,the thermo-elastic coeflicient, were determined by a torsion pendulumwhile the ambient temperature was changed through a series of values.,The proportionate change in moduli with temperature in relation to themoduli at 0 F. determines the temperature coefllcient.

For maximum mechanical properties, the alloys of the present inventionare preferably subjected ate cold working operation nd subsequently agedat temperatures between about 1100 F. and 1350 F. The usual solutiontreatment is acto a solution treatment prior to a modercomplished byheating at about 1700 F. to about 1750 F. and rapidly cooling, e. g.,oil quenching. Blow cooling from the aging temperatures is desirablefrom a standpoint of stability of properties.

Mere aging without cold working will increase the mechanical properties.Excellent high mechanical properties are obtained by cold working priorto the aging heat treatment and this treatment is ordinarily preferred.In some instances it may be convenient, particularly with alloyscontaining about 1.5% to 2% titanium,to cold work after aging heattreatment. Material cold worked-with or without prior aging, requires astress relief treatment to obtain stable thermoproperties; whereasexcessive amounts of cold work (75 to 99%) are necessary to produce highmechanical properties in Elinvar-type alloys.

For ordinary purposes a titanium content of about 2.4% to about 2.8% issatisfactory for high mechanical properties as shown in Table III.

05 elastic properties. Amounts of cold work up to about 35% or about 50%reduction in cross section which are readily attainable, appear verysuitable to produce excellent high mechanical Table III Y.s. 'r. s.cane. ma.

Alloy P. L.

Ordinary titanium-lree 84,000

Aged titaniumcontaming 123,000

159,000 0 ioxw 'I. S.- nsile stren th in pounds per square inch.

T. E. O.-thermo-e tic coelliclent per F.

M. R.-=modulus of rigidity in pounds per square inch. The ordinaryconstant modulus alloy, after water quenching from about 1750 F., wascold drawn 75% and treated for two hours at'about 650 F. The agehardened alloy (alloy 5) contained 42.4% nickel, 5% chromium, 2.4%titanium and balance iron including 0.06% carbon, 0.56% manganese, 0.56%silicon and impurities, and was water quenched from 1750 F.,subsequently cold drawn 35%, heat treated two hours at 1l50'F. andfurnace cooled.

High mechanical properties are obtained by aging at temperatures betweenabout 1100 and about 1350 F. However, byvarying the treatment withinthis range it is possible to vary the temperature coefllclent ofelasticity as'desired within certain ranges. For a given alloy, thehigher the aging temperature, the higher the temperature coefficient ofelasticity. Similarly, the longer the period of aging at a 'giventemperature, the higher the temperature co'efli'cient of elasticity.Also, it appears that the, more the cold work, the lower the temperaturecoeflicient of elasticity. Slow cooling fromthe aging temperatureusually resuits in appreciably higher proportional limits and morestable elastic properties. Table V shows the effect of varying thetreatment upon the properties of alloy 5. The material in each instancewas 'water quenched from 1750 F. prior .to receiving the varioustreatments shown in Table IV.

Table IV.

Cold Aging Aging Treatment work temp time '3 Cooling rate Percent F.Hours 35 l, 250 4 Furnace cooled. 35 1,150 4 Do. 35 1,150 2 Do. 50 1,1502 Do.

'I.E.G. M. R.

+15Xl0 l0. i 10 +l0 l0 10.0)(10' '0 10.0Xl0 '5 l0' 09x10 See Table IIIior k ey to symbols. v

The present invention provides a method of producing improved age'hardenable iron-nickelchromiurn-titanium alloys, and articles ofmanufacture made therefrom, possessing predetermined high mechanicalproperties and predetermined controlled modulus and containing asessential ingredients about 1% to about 4% titanium, about 36% to about47% nickel, a small but eilective amount up to about 9% chromium, and

the balance substantially iron, in which carbon may be present up toabout 0.2%, which comprises incorporating in an iron-nickel-chromiumalloy a selected titanium content within said range corresponding to thepredetermined desired mechanical properties, for example, proportionallimit, and being larger the higher said desired properties, the nickelcontent of said alloy being proportioned within said range in accordancewith the following formula:

Total Ni=Eflective Ni-i-K (Ti-4X0) where the effective nickel .isselected within the range of about 34.5% to about 37.5%, K being aconstant with a value of about 2.4, and Ni, Ti and C being respectivelythe weight percent of nickel, titanium and carbonfthe chromium contentof said alloy being proportioned within said range in accordance withthe following formula:

alloys provided by the present invention. Typical examples of suchdevices and elements or members include springs, for example, hairsprings for watches and other chronometers, springs for weighing scales;tuning forks; Bourdon tubes; proving rings for testing machines, torsionand tension dynamometers, etc.

We are aware of the invention described in U. S. patents to Pilling andMerica, including U. S. Patent No. 2,048,167, and we do not claim any ofthe subject matter disclosed therein. The present invention is animprovement in the art of controlled and constant modulusironnickel-chromium alloys.

Although the present invention has been described in conjunction withpreferred embodiments, it is understood that modifications andvariations may be resorted to without departing from the spirit andscope of the invention, as

those skilled in the art will readily understand;

We claim:

1. As an article of manufacture. an age hardenediron-nickel-chromium-titanium alloy possessing a temperature coeflicientof modulus of elasticity having a small positive to negative valueincluding zero and containing in weight percentage from 36% to 47%nickel; an eifective amount up to 9% chromium; 1% to 4% titanium; up to0.2 carbon; the percentage of nickel, titanium and carbon being suchthat Total NiK(Ti-4XC) Cr+(Ti4XC) lies between 4% and 9%, K being aconstant having a value of about 2.4%, and Ni, Cr, Ti and aaea ea Cbeing respectively nickel, chromium, titanium and carbon in weightpercentage; and the balance being substantially all iron whereby a novelage hardened iron-nickel-chromium-titanium alloy is obtained having aunique combination of properties including the aforesaid temperaturecoemcient of modulus of elasticity having a small positive to negativevalue including zero together with high mechanical properties.

2. As an article of manufacture, an age hardenediron-nickel-chromium-titanium alloy possessing a temperature coeillcientof modulus of elasticity having a small positive to negative valueincluding zero and containing in weight percentage from- 38.5% to 45.3%nickel; 4.7% to6% chromium; 2% to 3.25% titanium; up to 0.08%. carbon;the percentage of nickel, titanium and carbon. being such that TotalNi-K(Ti4 C) 7 lies between 34.5% and 37.5%, and the percentage ofohromium, titanium and carbon being such tha Cr+(Ti-4 C) lies between 7%and 8%, K beinga constant having a value of about 2.4, and' Ni, Cr, Tiand C being respectively nickel, chromium, titanium and carbon in weightpercentage; and the balance being substantially all iron whereby a novelage hardened iron-nickel-chromium-titanium alloy is obtained having auniqu combination of properties including the aforesaid temperaturecoefllcient of modulus of elasticity having a small positive to negativevalue including zero together with high mechanical properties.

3. As an article of manufacture, a resilient element made of an agehardened iron-nickelchromium-titanium alloy having the composition setforth in claim 4. As an article of manufacture, a precision deviceincluding a resilient element made of an age hardenediron-nickel-chromium-titanium alloy having the composition set forth inclaim 2.

5. As an article of manufacture, an age hardenableiron-nickel-chromium-titanium alloy possessing a temperature coefficientof modulus of elasticity having a small positive to negative valueincluding zero and containing in weight percentage from 38% to 47%nickel: an eifective amount upto 9% chromium; 1% to 4% titanium; up to0.2% carbon; the percentage of nickel, titanium and carbon being suchthe Total Ni'-K(Ti4xC) lies between 34.5% and 39%, and the percentageolfaohromium, titanium and carbon being such Cr+(Ti-4XC) lies betwen 4%and 9%, K being a constant having a value of about 2.4, and Ni, Cr, Tiand 0 being respectively nickel, chromium, titanium and carbon in weightpercentage; and the balance being substantially all iron whereby a novelage hardenable iron-nickel-chromiumtitanium alloy is obtained having inthe aged condition a unique combination of properties, including theaforesaid temperature coeillcient of modulus of elasticity having asmall positive to negative value including zero togetherwith highmechanical properties.

NORMAN B. BILLING. ALBERT M. TALBOT.

D cember 16, 19 1- nommn-B. PIiELIIGQ-ET AL.

'It is hereby certified that error p fi p enr-e -"lig tb rintedepecificatioo of the above numbered patent requiring.oornebtion'nffdliowE Page 1p, first column, line 75, claim 1 for "2.1;?read--Z'QlL-e; "and-that the' said Let 'ters Patent should be read withthis correction therein that the same may conform to the record ofltheeeise in'the latent Office.

Signed and sealed this 7th day of July A. 1912.

Patent No. 2,266, 4-82.

Henry Vati Aradale, (Seal) Acting comissioper' of Potenta.

